The present invention relates to a method of purifying a gas mixture containing undesirable gas compounds and more particularly to the elimination of undesirable compounds such as oxides of carbon, particularly carbon dioxide, the hydrogen and carbonyl sulfides and the alkylthiols.
In accordance with the present invention, the term gaseous mixture to be purified means a natural gas mixture such as natural gas, or a mixture of gases obtained in the course of chemical reactions, particularly in the refining industry. This gas mixture can contain, in particular, aside from at least one of the undesirable gas compounds cited above, hydrocarbons, and/or hydrogen.
Present methods of purifying gas mixtures generally involve one of the three operations below:
absorption by a liquid PA0 absorption by a solid PA0 chemical conversion, essentially in the presence of a catalyst. PA0 "chemical" solvents that extract the undesirable compounds by a chemical reaction, and restore them following a heating perhaps accompanied by a decompression, PA0 "physical" solvents that absorb the gases under pressure by dissolution in a liquid, and desorbing them by decompression. PA0 (a) a first stage of absorption with the aid of a solvent of the undesirable gas compounds, said first stage leading:
The first operation, which is often preferred, for the elimination from gas mixtures of undesirable compounds such as those defined above, involves two types of solvent, separately or in conjunction:
The physical solvents prove to be particularly interesting for gas mixtures brought under high pressure and containing a large percentage of undesirable compounds. Under these conditions, the "physical" solvents have greater absorption capacity than the "chemical" solvents. This advantage results in a lower proportion of solvent to be used, a reduction in the size of the equipment, and in the cost of utilities.